JP4407689B2 - Heat pump water heater - Google Patents

Description

The present invention relates to a heat pump water heater, and more particularly to a heat pump water heater that uses carbon dioxide (CO ₂ ) as a refrigerant.

The conventional refrigeration and air-conditioning apparatus uses CO ₂ as a refrigerant, and includes a compressor, a gas cooler, a high-low pressure heat exchanger, an expansion means, an evaporator, and a low-pressure refrigerant receiver, and adjusts the gas cooler outlet refrigerant temperature by the expansion means. (For example, refer to Patent Document 1). Moreover, some conventional heat pump water heaters include a compressor, a radiator, an expansion means, and an evaporator, and the discharge temperature is controlled by the expansion means (see, for example, Patent Document 2). The conventional refrigeration and air-conditioning apparatus uses CO ₂ as a refrigerant, and includes a compressor, a gas cooler, a high-low pressure heat exchanger, an expansion means, and an evaporator. The high-pressure side pressure is increased by the expansion means of the high-low pressure heat exchanger refrigerant circuit. Some are adjusted (for example, see Patent Document 3).

Japanese Patent No. 2931668 (page 2-3, FIG. 3) JP 2004-340535 A (page 4-6, FIG. 1) Japanese Patent Laying-Open No. 2005-315558 (pages 10-11, FIG. 12)

  Since the conventional refrigeration air conditioner has a high and low pressure heat exchanger, the compressor suction refrigerant can be converted into superheated gas, and the compressor reliability can be improved because the liquid refrigerant is not sucked into the compressor. Moreover, since the conventional heat pump water heater controls the discharge temperature by the expansion means, it is possible to avoid an excessive temperature rise of the compressor and improve the compressor reliability.

However, in the case of a hot water supply device, it is necessary to always supply hot water at a temperature desired by the user, and when viewed from the refrigeration cycle, it is specified to a predetermined value that targets the heating ability to heat the water on the load side to hot water. There was a problem that it was required to maintain the ability to heat hot water at a high temperature. On the other hand, as a result of evaluating a refrigerant circuit that combines a conventional apparatus and uses a high-low pressure heat exchanger to control the discharge temperature with expansion means, and controls the discharge temperature to a target value, It was found that there are multiple stable states. As an example, when the discharge temperature and the heating capacity when the expansion valve opening is changed are investigated, as shown in FIG. 2, when the expansion valve opening is A, a predetermined capacity can be obtained. When the degree is B, the predetermined ability cannot be obtained. That is, in a refrigerant circuit including a high-low pressure heat exchanger, there is a problem that a predetermined capacity cannot always be obtained when the discharge temperature is controlled by the expansion valve.

  The present invention has been made in order to solve the above-described problems. It is an object of the present invention to control discharge temperature with expansion means and obtain a predetermined heating capacity in a heat pump water heater including a high-low pressure heat exchanger. And

The heat pump water heater according to the present invention includes a radiator that exchanges heat between the high-pressure refrigerant discharged from the compressor and water , a first expansion valve that depressurizes the high-pressure refrigerant from the radiator, and a pressure reduction by the first expansion valve. An evaporator that evaporates the generated low-pressure refrigerant is connected in a ring shape, a refrigeration cycle that circulates the refrigerant, a hot water supply circuit that circulates water heated by a radiator by a pump and stores it in a tank, and heat dissipation by the hot water supply circuit a hot water temperature control means for controlling the detected target hot water temperature of the hot water temperature is the temperature of the heated water in the vessel, connected to the inlet side of the branched evaporator from between radiator and the first expansion valve of the refrigeration cycle And a high temperature for exchanging heat between the branch flow path in which the second expansion valve is arranged on the downstream side, and the refrigerant in the high pressure branch flow path arranged on the upstream side of the branch flow path and the low-pressure refrigerant from the evaporator. Discharge temperature detector that detects the discharge temperature of the low-pressure heat exchanger and high-pressure refrigerant A discharge temperature control means for controlling the detected discharge temperature to the target discharge temperature, and a stable state for determining that at least one of the refrigerant state of the refrigeration cycle and the hot water temperature of the hot water supply circuit is in a stable state Determining means for determining that the stable state determining means is in a stable state, and increasing the heating capacity of the radiator when the heating capacity in the stable state is insufficient for a predetermined capacity.

  According to the heat pump water heater of the present invention, in the refrigerant circuit having the high and low pressure heat exchanger, there is an effect that the discharge temperature is controlled by the discharge temperature control means and a predetermined heating capacity can be obtained.

Embodiment 1 FIG.
A first embodiment of the present invention is shown in FIG. FIG. 1 is a refrigerant circuit diagram of a heat pump water heater of the present invention. In the heat pump unit 1, a compressor 3, a radiator 4, a first expansion valve 5, and an evaporator 6 are sequentially connected in an annular manner to circulate the refrigerant. A refrigeration cycle arranged outdoors, a fan 7 that blows outside air sucked into the evaporator 6 from outside, and a branch from the radiator 4 to the first expansion valve 5, evaporating from the first expansion valve 5. The high- and low-pressure heat exchanger 9 and the second expansion valve 10 disposed on the branch flow path 8 connected to the pipe leading to the heater 6, and the load-side medium heated by the radiator 4 in the hot water supply circuit On the other hand, a tank 12 for storing hot water heated via the radiator 4 by the pump 11 is mounted in the tank unit 2.

The high-low pressure heat exchanger 9 is, for example, a double-tube heat exchanger, or may be configured such that the low-pressure side pipe and the high-pressure side pipe are brought into external contact and brazed. The flow direction of the refrigerant is preferably counterflow. In the refrigerant circuit diagram of the heat pump water heater of FIG. 1, a hot water supply device that supplies hot water having a constant temperature stored in the tank from the tank 12 of the hot water supply circuit to a bath or the like is omitted. The circuit for supplying water is also omitted from the hot water supply circuit of FIG. In addition, the explanation will be made assuming that the rotation speed is variable by using an inverter-controlled DC brushless motor as a compressor drive so that the pressure and temperature of the high-pressure refrigerant discharged as a compressor can be changed. A plurality of compressors may be combined and this combination may be switched to make the overall capacity variable. In addition, a structure such as a suction muffler that reduces refrigerant noise is provided on the suction side of the compressor, and a device that collects the lubricating oil that has flowed out is provided on the discharge side of the compressor. It does not matter if it is added. That is, FIG. 1 illustrates only the basic circuit of a heat pump water heater. As a refrigerant to be circulated in the refrigeration cycle of this heat pump water heater, a natural refrigerant, for example, carbon dioxide (CO ₂ ), which is easily available since the high pressure side in the refrigeration cycle becomes a supercritical state at a critical pressure (about 73 kg / cm ² ) or higher. Used.

  In the heat pump unit 1, in the hot water supply circuit, the water supply temperature sensor 13a is provided on the water inlet side of the radiator 4 on the water supply side, and the hot water discharge temperature sensor 13b is provided on the water outlet side heated by the radiator 4. Measure the water temperature at each installation location. In addition, an outside air temperature sensor 13 c provided at or near the heat pump unit 1 measures the outside air temperature around the heat pump unit 1. In the refrigerant circuit in which the refrigerant circulates, the discharge temperature sensor 13d is provided on the outlet side of the compressor 3, the suction temperature sensor 13e is provided on the inlet side of the compressor 3, and the evaporation temperature sensor 13f is provided on the intermediate portion from the inlet of the evaporator 6. Measure the refrigerant temperature.

  A measurement control device 14 is provided in the heat pump unit 1. The measurement control device 14 is based on the measurement information from each temperature sensor 13 and the content of operation command information instructed by a heat pump water heater user by a remote control device or the like. 5, the opening of the second expansion valve 10, the operation method of the pump 11, and the like.

  Next, the operation of the heat pump water heater will be described. In the refrigeration cycle of the heat pump unit 1, the high-temperature and high-pressure gas refrigerant discharged from the compressor 3 is lowered in temperature while radiating heat to the hot water supply circuit 2 side by the radiator 4. At this time, if the high-pressure side refrigerant pressure is equal to or higher than the critical pressure, the refrigerant radiates heat at a reduced temperature without undergoing a gas-liquid phase transition in a supercritical state. If the high-pressure side refrigerant pressure is equal to or lower than the critical pressure, the refrigerant radiates heat while liquefying. Hot water supply heating is performed by applying heat radiated from the refrigerant to a load side medium such as water on the load side (hot water supply circuit). The high-pressure and low-temperature refrigerant that has flowed out of the radiator 4 through hot water heating is branched into a flow path that passes through the first expansion valve 5 and a flow path that passes through the branch flow path 8.

The refrigerant that has passed through the first expansion valve 5 is decompressed to a low-pressure gas-liquid two-phase state. The high-pressure refrigerant that has passed through the branch flow path 8 passes through the high-pressure side flow path of the high-low pressure heat exchanger 9 and flows through the low-pressure side flow path of the high-low pressure heat exchanger 9 that flows out of the evaporator 6 and heat. After being exchanged and cooled, the pressure is reduced to a low-pressure gas-liquid two-phase state through the second expansion valve 10. The refrigerant that has passed through the first expansion valve 5 and the refrigerant that has passed through the second expansion valve 10 merge before flowing into the evaporator 6 and flow into the evaporator 6 where they absorb heat from the outside air and are evaporated and gasified. The The low-pressure refrigerant exiting the evaporator 6 passes through the high-low pressure heat exchanger 9 and exchanges heat with the high-pressure refrigerant passing through the high-pressure side flow path to be superheated gas, and is sucked into the compressor 3 and circulated to be refrigerated cycle. Form.

  On the hot water supply circuit side, the heat radiated from the refrigerant by the radiator 4 is guided from the lower part of the tank 12 by the pump 11 provided on the inflow side of the radiator 4 to the hot water supply circuit side of the radiator 4. It is given to a load side medium such as water to be conveyed. The heated load-side medium flows in from the upper part of the tank 12 and is stored in the tank 12. That is, the upper part of the tank is hot water and the lower part is water.

  Next, the operation control operation in this heat pump water heater will be described. The heat pump water heater operates based on a predetermined capacity necessary for heating water as a load with a radiator and a preset target hot water temperature. The predetermined capacity is set so that, for example, the output value of the compressor is a constant value based on the operation command information instructed by the user from the remote controller. The target hot water temperature is set from the operation command information instructed by the remote controller from the user, or the heat storage energy calculated from the past hot water use amount in the remote controller or by the microcomputer provided in the measurement control device 14 is used. It is set so that it can be secured. Further, the target hot water temperature has a predetermined range, for example, a range of 65 ° C. to 90 ° C.

  The rotation speed of the compressor 3 is controlled so that a predetermined capacity is obtained at the target hot water temperature. Since the feed water temperature flowing in from the bottom of the tank is supplied at a substantially constant temperature until the completion of boiling, the load is operated at a substantially constant once the target hot water temperature is determined. If the predetermined capacity can be secured at the maximum value required for heating in the target hot water temperature range, the predetermined capacity can be secured within the target hot water temperature range. Therefore, the rotation speed of the compressor 3 which is the heating capacity of the radiator 4 can be ensured at any target hot water temperature by, for example, a function of the outside air temperature and the feed water temperature. In other words, the output of the compressor is prepared with the ability to ensure the hot water temperature required as a water heater at any time for any external conditions. As a result, hot water at the desired temperature is always used as a water heater. Obtainable. Although the number of compressors 3 is one in the figure, a plurality of units may be connected in parallel or in series. In that case, in addition to the number of rotations of the compressor 3, the number of operating units is controlled to ensure the capacity. be able to. Moreover, the rotation speed of the compressor 3 is provided with an upper limit rotation speed and a lower limit rotation speed in order to ensure compressor durability in consideration of maintaining reliability when a long-term operation is continued.

  The opening degree of the second expansion valve 10 is controlled so that the discharge temperature becomes a predetermined value (target discharge temperature). The target discharge temperature is set to a temperature higher than the target hot water temperature, that is, the target hot water temperature + α [deg], in order to make the target hot water temperature secureable. The value α is, for example, a function of the outside air temperature or the target hot water temperature. Thus, the required hot water temperature can be ensured by setting it as the target discharge temperature according to the target hot water temperature. Also, from the viewpoint of compressor durability and refrigeration machine oil degradation, an upper limit temperature is usually provided for the discharge temperature.

  From the viewpoint of the reliability of the compressor 3, the opening of the first expansion valve 5 is sufficient in the high-low pressure heat exchanger 9 in order to keep the refrigerant sucked into the compressor 3 as superheated gas instead of being liquid refrigerant. It is closed during normal operation so that it can be heated. However, when the target discharge temperature is operated near the upper limit value, or when the rotation speed of the compressor 3 is operated near the upper limit value, for example, when the outside air temperature is low and the target hot water temperature is high, There is a case where the ability is insufficient. Further, when the outside air temperature is low and the evaporation temperature of the evaporator 6 is 0 ° C. or less, the evaporator 6 is frosted and its capacity is reduced, so that it is necessary to perform a defrosting operation. During the defrosting operation, since the pump 11 is stopped and no heating capacity is generated, the average heating capacity is lowered.

  In such a case, by opening the opening of the first expansion valve 5, the heat exchange amount of the high / low pressure heat exchanger 9 is decreased, and the suction superheat degree of the refrigerant sucked into the compressor 3 is decreased. That is, the suction refrigerant density of the compressor 3 increases due to a decrease in the degree of suction superheat, and the amount of refrigerant circulation increases, so the heating capacity increases. That is, depending on the external conditions, the opening degree of the first expansion valve 5 is controlled as a function of, for example, the outside air temperature and the target boiling temperature.

  The rotation speed of the pump 11 is controlled so that the tapping temperature becomes the target tapping temperature. Since the discharge temperature is controlled to the target hot water temperature + α [deg] by the second expansion valve 10, that is, the heating capacity on the refrigeration cycle side is maintained constant, the hot water temperature can be reliably ensured. Each of the above controls, heating capacity control based on the number of rotations of the compressor, and hot water temperature control based on the second expansion valve opening degree, etc. are individually controlled based on the respective parameters.

  FIG. 2 is a diagram for explaining an example of control contents in the heat pump water heater of the present invention. The second expansion is performed in a state where the first expansion valve opening degree, the compressor rotation speed, and the pump rotation speed are constant. It is the data which shows the change state characteristic of the refrigerant | coolant in each site | part which measured by providing each measuring device in the refrigerating cycle by changing the opening degree of the valve 10 like a horizontal axis. The top of the vertical axis in FIG. 2 is the heating capacity (kW) of the refrigerant through which the radiator 4 passes the opening degree of the second expansion valve 10 as the load-side medium, and is obtained from the tapping temperature and the amount of water. As shown in the figure, the heating capacity does not change so much until the opening degree is X, but when it exceeds that, the heating capacity becomes insufficient and rapidly decreases. The second high-pressure side pressure (MPa) from the top is the pressure of the high-pressure refrigerant compressed by the compressor 3, and gradually decreases as the opening degree increases. Compared with the opening degree A of the second expansion valve 10, the high pressure side pressure of the refrigerant is lower at the opening degree X and the opening degree B. The third temperature from the top is the refrigerant temperature (° C.) corresponding to the opening at the radiator outlet and the compressor suction position, and the temperature rises when the opening is increased. The fourth from the top is the discharge temperature of the compressor, which is the refrigerant temperature detected by the discharge temperature sensor 13d when discharged from the compressor 3, and a target value is set. It is shown that the target value is reached at the opening degree B, but is low at the opening degree X and above the target value at the opening degree B or higher. At the bottom, the horizontal axis represents the opening of the second expansion valve 10 and the vertical axis represents the suction superheat (deg) of the compressor. It is obtained from the difference between the temperature information from the suction temperature sensor 13e and the temperature information from the evaporation temperature detection sensor 13f. The suction temperature sensor can be obtained by replacing it with an evaporator outlet or a high / low pressure heat exchanger outlet.

  From FIG. 2, when the discharge temperature is controlled by the second expansion valve 10, there are cases where there are at least two stable states at the same discharge temperature depending on the operating conditions, and the state is controlled to a state B where a predetermined capacity cannot be obtained. I understand that there is. In other words, simply controlling the discharge temperature so as to match the target value does not provide the ability to heat the hot water required by the user because the heating ability is insufficient. In other words, it can be seen that even if a hot water temperature that is substantially the same as the discharge temperature is detected, the capacity is insufficient and a problem occurs as a hot water supply device. That is, even if at least one of the discharge temperature and the tapping temperature reaches the target value, the necessary heating capacity cannot be lowered, and the amount of hot water stored in the tank 12 cannot be obtained. It causes problems such as coming.

  FIG. 3 is a characteristic diagram showing the operating state of the refrigeration cycle. The vertical axis is pressure (P), the horizontal axis is enthalpy (H), and the solid line is the heating capacity of the opening A and maintains the target value. In the refrigeration cycle operation state, the broken line indicates an operation state in which the heating capacity at the opening degree B is small and has not reached the predetermined heating capacity. As shown in FIG. 2, the opening degree B is larger than the opening degree A, and the degree of suction superheat, which is the difference between the saturation temperature obtained from the suction temperature and the suction pressure of the compressor, is larger in the opening degree B. It has become. When compression is performed from a state where the suction superheat degree is different, when the discharge temperature is the same, the compression from the opening degree B where the suction superheat degree is large is lower than the opening degree A where the predetermined heating ability is obtained, both in the heating capacity and the high pressure. It shows driving in the state. Therefore, when the tapping temperature and the discharge temperature reach the target values and the operation state is stabilized, the detected suction superheat degree is compared with the predetermined suction superheat degree β, that is, if it is higher than the predetermined suction superheat degree, a predetermined value is obtained. It can be determined that the ability of is not obtained. The predetermined suction superheat degree β is, for example, a function of the outside air temperature or the target hot water temperature.

  Heating that can maintain the temperature of hot water that requires a radiator without reaching the required heating capacity even if at least one of the discharge temperature and tapping temperature reaches the target value. As a capability determination means for determining whether or not the capability has been obtained, the structure for determining and determining the compressor intake superheat degree has been described. However, as shown in the relationship explanatory diagram with respect to the opening degree in FIG. A detector may be provided to monitor the pressure, or a radiator outlet temperature detector may be provided to detect and determine that the radiator outlet temperature is not too high. Furthermore, the flow rate of the hot water supply circuit together with the temperature of the hot water may be monitored by the number of revolutions of the pump, etc., and the heating capacity may be determined by calculation.

  Next, the operation of shifting to the state A for obtaining the predetermined ability when the state becomes stable in the state B where the predetermined ability cannot be obtained, that is, when the detected suction superheat degree is larger than the predetermined suction superheat degree will be described. This operation is executed according to a control flow set in a microcomputer provided in the measurement control device 14. This control flow is shown in the flowchart of FIG. In FIG. 4, ST1 is a step of starting a flow for determining a refrigeration cycle operation including control of a heating capacity recovery control means provided in the measurement control device 14 to recover the heating capacity to a predetermined capacity, and ST2 is rotation of the compressor The step of controlling the number of revolutions by a microcomputer to a rotational speed set in accordance with ambient environmental conditions as measured by the outside air temperature sensor 13c, ST3 is adjusted to the target hot water temperature of the pump 11 of the hot water supply circuit. A step of rotating by the control device 14, ST4 is a step of setting the discharge temperature to an opening controlled by the control device 14 in accordance with the target discharge temperature, and ST5 is whether the capacity is insufficient after reaching a stable state Is a step of determining whether or not the ability recovery operation is being carried out, and if the ability recovery operation is entered, Since a flag 1 for example at step ST8 that will be described later by the control flow of the microcomputer has become as can be determined by this flag. ST6 is a step of determining by the microcomputer of the control device 14 whether or not this state stability is continued by the stable state determination means from the state of the refrigerant or the tapping temperature, and ST7 is a capacity determination means provided in the control device 14. Step ST8 is a step for determining whether or not the suction superheat degree is equal to or greater than a predetermined value, and ST8 is a step for starting capacity operation. If the flag is zero, it is replaced with 1. ST9 is a step of increasing the opening degree of the first expansion valve 5 little by little by the capacity recovery control means provided in the control device 14, for example, a step of increasing γ degrees first, and ST10 is a discharge temperature to be detected is a target discharge temperature. ST11 is a step of decreasing the opening of the first expansion valve, and ST12 is a step of ending the capacity recovery operation, returning the flag from 1 to zero.

  The operation of the control flow in FIG. 4 will be described. When the heating operation is started (ST1), measurement control is performed based on at least the set predetermined heating capacity, the outside air temperature detected by the outside air temperature sensor 13c, each information obtained by the feed water temperature sensor 13a and the hot water temperature sensor 13b. The rotation speed of the compressor 3 is set to be larger than necessary in the device 14, and similarly, the rotation speed of the pump 11 and the opening of the second expansion valve 10 are controlled with respect to the respective target values (ST2, ST3, ST4). The control operation is continued until the target value is reached, that is, until the operation state is stabilized (ST5, ST6, ST7). When it is determined that the state is not stable, the control to the target value set in accordance with the ambient environment stored in the microcomputer in advance is returned to Step 2 and repeated.

  After the operating state is stabilized, if the suction superheat degree is equal to or higher than the predetermined suction superheat degree β, that is, if it is determined that the heating capacity is insufficient, the capacity recovery operation is performed (ST7, ST8). If it is determined that the heating capacity has a predetermined capacity, the operation for maintaining the heating of the target values of the normal compressor 3 and the second expansion valve 10 is continued (ST2, ST3, ST4). When the capacity recovery operation is started (ST7, ST8), the opening of the first expansion valve 5 is γ-opened (ST9). By opening the opening of the first expansion valve 5, the discharge temperature of the compressor 3 decreases, and when the second expansion valve 10 controls the target discharge temperature, the opening of the second expansion valve 10 decreases. At the same time, the rotational speed of the pump 11 is increased by controlling the hot water temperature of the pump 11.

  If the difference between the target discharge temperature and the discharge temperature is equal to or less than δ (ST10), the opening degree of the first expansion valve 5 is closed by γ (SY11), and the capacity recovery operation is terminated (ST12). Subsequently, the discharge temperature control of the second expansion valve 10 is continued (ST2, ST3, ST4), and when the discharge temperature reaches the target discharge temperature, the opening degree of the second expansion valve 10 is not changed as shown in FIG. Since the rotational speed of the pump 11 is also increased, the capacity is increased, and a state A in which a predetermined capacity is obtained is obtained.

  The above target values are all functions of a specific temperature. However, a predetermined map may be stored and set as a target value corresponding to the map. Moreover, although the temperature to be referred to is specified and described as an example, it can be replaced with other environmental conditions. Therefore, the discharge temperature control with the second expansion valve 10, the tapping temperature control with the pump 11, the capacity control with the compressor 3, and the capacity recovery control with the first expansion valve 5 are always requested by the user according to the environmental load conditions. It is possible to realize the operation of the heat pump water heater that can maintain the predetermined capacity corresponding to the above.

  In the case of heat pump hot water supply, the refrigeration cycle is usually heated to a set temperature while maintaining a predetermined heating capacity using a night time zone. Even after boiling, the ability recovery control described in the flowchart of FIG. 4 is performed to prepare for maintaining the tapping temperature at the target value. However, it is not always necessary to maintain the same heating capacity depending on the hot water supply device or the time zone in which the use time zone is fixed, such as a bath. In such a case, if the predetermined heating capacity can be switched between large and small according to use (temperature) and time period, the effect is great as an energy saving measure. Such switching of the setting of the heating capacity may be set by a remote controller used by the user, or may be stored in a microcomputer of the measurement control device and automatically switched. When a low heating capacity that is not frequently used is selected, the capacity recovery operation described in FIG. 4 is not performed, and the capacity recovery operation can be performed when switching to a large heating capacity. In other words, it is possible to obtain a heat pump water heater that can select whether or not to perform the capacity recovery operation (step 5 to step 12 in FIG. 4).

  The heat pump water heater of the present invention includes a compressor that compresses a refrigerant to a supercritical pressure, a heat exchanger that exchanges heat between a high-temperature and high-pressure refrigerant discharged from the compressor and a load-side medium such as water, and a first depressurizing refrigerant. The hot water supply which connects the expansion valve of 1 and an evaporator cyclically, stores the load side medium heated by the refrigerant | coolant which distribute | circulates a refrigerant | coolant, and the refrigerant | coolant which distribute | circulates a radiator in a tank, and uses it for hot water supply like a bath A branch flow connected to the inlet side of the evaporator by branching from the circuit, a pump provided on a hot water supply circuit that circulates water such as tap water and water in the tank, and a radiator and an expansion valve A high-low pressure heat exchanger that exchanges heat between the high-pressure refrigerant in the branch flow path and the low-pressure side refrigerant in the main flow path, and a downstream of the high-low pressure heat exchanger in the branch flow path. Second expansion valve and discharge temperature for detecting compressor discharge temperature Intelligent means, suction superheat degree detecting means for detecting compressor superheat degree, discharge temperature control means for controlling discharge temperature to target discharge temperature, tapping temperature control means for controlling tapping temperature to target tapping temperature, heating Capacity control means for controlling the capacity to a predetermined capacity and the operation of the refrigeration cycle, the discharge temperature becomes the target discharge temperature, or the tapping temperature reaches the target value, or both reach the target and become stable. The stable state determining means for determining that the stable state determining means is determined to be in the stable state, the ability determining means for determining whether the heating capacity in the stable state is a predetermined capacity, and the capability determining means are determined to be insufficient in capacity. In this case, a capability recovery control means for controlling the heating capability to a predetermined capability is provided.

  The stable state determination means of the heat pump water heater of the present invention determines that the discharge temperature control means is in the stable state when the discharge temperature becomes the target discharge temperature and the discharged hot water temperature control means reaches the target hot water temperature. Note that hot water having a tapping temperature is stored in the upper part of the hot water supply circuit, and hot water supplied to a hot water supply device such as a bath is supplied by mixing the stored hot water and water.

  The capability determination means of the heat pump water heater of the present invention has been described by determining that the capability is insufficient when the suction superheat degree detected by the suction superheat degree detection means is larger than a predetermined value as an example. It is possible to estimate from the whole refrigerant state, and it is only necessary to provide a detecting means necessary for that purpose or use another sensor.

  The capacity recovery control means of the heat pump water heater of the present invention is a first expansion valve provided in the refrigeration cycle. The capacity control means of the heat pump water heater of the present invention determines the rotational speed of the compressor from information on at least a predetermined heating capacity, the outside air temperature, and the feed water temperature.

  Although the description has been made with the configuration in which the capacity recovery control means for recovering the heating capacity is the first expansion valve and the speed of the compressor is variable as the capacity control means for constantly maintaining the heating capacity, this configuration is not necessarily required. For example, a configuration in which a circuit having a circuit configuration capable of cutting the capability by combining a plurality of compressors may be switched. Further, an auxiliary device such as an expansion mechanism or an ejector that assists the pressure of the compressor may be provided during the refrigeration cycle, and these auxiliary devices may be controlled or switched.

  The discharge temperature control means of the heat pump water heater of the present invention determines the target discharge temperature from information on at least the outside air temperature and the target hot water temperature.

  The heat pump water heater of the present invention includes a compressor that compresses a refrigerant to a supercritical pressure, a radiator that exchanges heat between the refrigerant discharged from the compressor and a load-side medium, an expansion valve that decompresses the refrigerant, and an evaporator. A refrigeration cycle in which the refrigerant circulates, a hot water supply circuit that stores a load-side medium heated by the refrigerant flowing through the radiator in a tank, a pump provided on the hot water supply circuit, a radiator, and the expansion High and low pressure heat that is provided in a branch flow path that branches from between the valves and is connected to the inlet side of the evaporator and that exchanges heat between the high pressure refrigerant in the branch flow path and the low pressure side refrigerant in the main flow path An exchanger, a second expansion valve arranged on the downstream side of the high and low pressure heat exchanger of the branch flow path, a discharge temperature detecting means for detecting the compressor discharge temperature, and a discharge for controlling the discharge temperature to the target discharge temperature Temperature control means and control the tapping temperature to the target tapping temperature A hot water temperature control means and a capacity control means for controlling the heating capacity to a predetermined capacity are provided, and the capacity control means compresses from information on at least the predetermined capacity, the outside air temperature, and the feed water temperature. Determine the speed of the machine.

  The heat pump water heater of the present invention includes a compressor that compresses a refrigerant to a supercritical pressure, a radiator that exchanges heat between the refrigerant discharged from the compressor and a load-side medium, an expansion valve that decompresses the refrigerant, and an evaporator. A refrigeration cycle in which the refrigerant circulates, a hot water supply circuit that stores a load-side medium heated by the refrigerant flowing through the radiator in a tank, a pump provided on the hot water supply circuit, a radiator, and an expansion valve High-low pressure heat exchange that is provided in a branch flow path that branches from between the two and is connected to the inlet side of the evaporator and that exchanges heat between the high-pressure refrigerant in the branch flow path and the low-pressure refrigerant in the main flow path , A second expansion valve disposed on the downstream side of the high / low pressure heat exchanger of the branch flow path, discharge temperature detecting means for detecting the compressor discharge temperature, and discharge temperature for controlling the discharge temperature to the target discharge temperature Control means and outlet for controlling the tapping temperature to the target tapping temperature A temperature control means, and capacity control means for controlling the heating capacity to a predetermined capacity, discharge temperature control means determines at least the outside air temperature, and the target outgoing hot water temperature, from the information, the target discharge temperature.

  Since the heat pump water heater of the present invention has a high-low pressure heat exchanger, the refrigerant sucked from the compressor can be superheated and the compressor reliability can be improved. Moreover, since this heat pump water heater controls the discharge temperature by the expansion means, it is possible to avoid an excessive temperature rise of the compressor and improve the compressor reliability. However, as a result of evaluating the refrigerant circuit that controls the discharge temperature by the expansion means using the high and low pressure heat exchanger, when the discharge temperature is controlled to the target value, there are a plurality of stable states for the same discharge temperature, which are not always predetermined. There is a problem that ability cannot be acquired, and this problem is solved. That is, a compressor that compresses the refrigerant to a supercritical pressure, a radiator that exchanges heat between the refrigerant discharged from the compressor and the load-side medium, an expansion valve that decompresses the refrigerant, and an evaporator are connected in an annular shape, A refrigeration cycle that circulates, a hot water supply circuit that stores a load-side medium heated by refrigerant flowing through the radiator in a tank, a pump provided on the hot water supply circuit, and a branching and evaporation from the radiator and the expansion valve A high-low pressure heat exchanger that is provided in a branch channel connected to the inlet side of the vessel and exchanges heat between the high-pressure refrigerant in the branch channel and the low-pressure side refrigerant in the main channel; A second expansion valve disposed downstream of the high-low pressure heat exchanger, a discharge temperature detecting means for detecting the compressor discharge temperature, a suction superheat degree detecting means for detecting the compressor suction superheat degree, and a discharge temperature. Discharge temperature control means for controlling to the target discharge temperature and tapping temperature A hot water temperature control means for controlling the target hot water temperature, and capacity control means for controlling the heating capacity to a predetermined capacity, but with the.

The heat pump water heater of the present invention has each control, as described above, heating capacity control based on the number of rotations of the compressor, hot water temperature control based on the second expansion valve opening degree, and suction overheating based on the first expansion valve opening degree. Since a plurality of controls are controlled independently for each target based on each parameter independently, the refrigerant state and the hot water temperature are in a plurality of states of the second expansion valve opening degree. There is a problem that it is stable and cannot be maintained at the desired opening, and reliability is determined by determining whether or not these stable states such as the state of the refrigerant and the temperature of hot water can obtain the required heating capacity, and further recovering the capacity A device with high accuracy can be obtained.

The refrigerant used in the refrigeration cycle of the present invention is described as an example in which a refrigerant that can be in a supercritical state, such as carbon dioxide, is used, but this is useful as a countermeasure for the global environment.

It is a refrigerant circuit figure of the heat pump water heater which concerns on Embodiment 1 of this invention. It is a figure showing the operating condition of the heat pump water heater when changing the 2nd expansion valve 10 concerning Embodiment 1 of the present invention. It is a PH diagram showing the driving | running state of the heat pump water heater when the 2nd expansion valve 10 which concerns on Embodiment 1 of this invention is changed. It is a flowchart of the capability recovery control which concerns on Embodiment 1 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Heat pump unit, 2 Tank unit, 3 Compressor, 4 Heat radiator, 5 1st expansion valve, 6 Evaporator, 7 Fan, 8 Branch flow path, 9 High-low pressure heat exchanger, 10 2nd expansion valve, 11 Pump, 12 tanks, 13 temperature sensor, 14 measurement control device.

Claims (7)

A radiator that exchanges heat between the high-pressure refrigerant discharged from the compressor and water , a first expansion valve that decompresses the high-pressure refrigerant from the radiator, and evaporates the low-pressure refrigerant decompressed by the first expansion valve A refrigerating cycle in which the evaporator is connected in a ring and the refrigerant is circulated;
A hot water supply circuit that circulates the water heated by the radiator by a pump and stores it in a tank;
A tapping temperature control means for detecting a tapping temperature which is a temperature of water heated by the radiator in the hot water supply circuit and controlling it to a target tapping temperature;
A branch flow path branching from between the radiator and the first expansion valve of the refrigeration cycle and connected to the inlet side of the evaporator, and a second expansion valve disposed on the downstream side;
A high-low pressure heat exchanger that is arranged upstream of the branch flow path and exchanges heat between the high-pressure refrigerant in the branch flow path and the low-pressure refrigerant from the evaporator;
A discharge temperature control means for detecting a discharge temperature of the high-pressure refrigerant by a discharge temperature detection means and controlling the detected discharge temperature to a target discharge temperature;
Stable state determination means for determining that at least one of the refrigerant state of the refrigeration cycle and the hot water temperature of the hot water supply circuit is in a stable state,
The heat pump water heater according to claim 1, wherein the stable state determining means determines that the stable state is satisfied, and the heating capacity of the radiator is increased when the heating capacity in the stable state is insufficient for a predetermined capacity.   The stable state determining means determines that the stable state is obtained when the discharge temperature becomes the target discharge temperature by the discharge temperature control means and the hot water temperature becomes the target hot water temperature by the hot water temperature control means. The heat pump water heater according to claim 1.   When the stable state determining means determines that the stable state, and when it is determined that the heating capacity in the stable state is insufficient for the predetermined capacity, the capacity recovery control means for controlling the heating capacity of the radiator to the predetermined capacity, The heat pump water heater according to claim 1 or 2, wherein the capacity recovery control means is the first expansion valve provided in the refrigeration cycle.   Capability judging means for judging whether or not the heating capacity of the radiator has a predetermined ability is provided, and as this ability judging means, a suction superheat degree detecting means for detecting a compressor suction superheat degree, a pressure of a high-pressure refrigerant is detected. Use at least one of high pressure refrigerant pressure detection means, heat radiator outlet refrigerant temperature detection means for detecting the temperature of the radiator outlet refrigerant, and capacity calculation means for calculating the heating capacity by detecting the flow rate of the hot water supply circuit. The heat pump water heater according to claim 1, claim 2, or claim 3.   The heat pump water heater according to any one of claims 1 to 4, wherein the number of rotations of the compressor is determined from information on at least a predetermined capacity, an outside air temperature, and a feed water temperature.   The heat pump water heater according to any one of claims 1 to 4, wherein the discharge temperature control means determines a target discharge temperature from at least information of an outside air temperature and a target hot water temperature. The heat pump water heater according to any one of claims 1 to 6 , wherein the refrigerant used in the refrigeration cycle is carbon dioxide.

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